This invention relates to methods of forming conductive connections, methods of reducing oxidation, oxidation protection methods, methods of forming integrated circuit structures, such as conductive interconnects and wire bonds, and integrated circuits formed thereby.
Several advantages exist for using copper metalization in integrated circuits, such as semiconductor devices. However, copper metalization may be more susceptible to oxidation under certain process conditions as compared to other metals, such as aluminum. Semiconductor devices often include at least two primary metal layers with interconnections between such layers. The first metal layer can be a so-called xe2x80x9cmetal 1xe2x80x9d layer and the second can be a so-called xe2x80x9cmetal 2xe2x80x9d layer.
The first metal layer may be formed on a substrate and covered by a dielectric material, such as silicon dioxide. An opening for an interconnect may then be formed through the dielectric material to expose the first metal layer. The opening may be formed by patterning a layer of photoresist deposited over the dielectric and etching portions of the dielectric material exposed through the photoresist. A common process for removing photoresist comprises ashing. Such removal of a photoresist exposes the first metal layer to the ashing conditions, potentially oxidizing the first metal layer. Copper is particularly susceptible to oxidation at high temperature processing, such as processing at 200xc2x0 C. or higher.
One method for reducing oxidation of the first metal layer includes forming a layer of silicon nitride over the first metal layer prior to forming dielectric material over the first metal layer. The dielectric material is then processed as indicated above with formation of a photoresist, patterning of the photoresist, etching, and photoresist removal by ashing. However, after etching an opening for a conductive interconnect, a separate etch of the silicon nitride may be used to expose the first metal layer preparatory to forming a conductive interconnect to such layer. A high level of selectivity may often be provided for etching the silicon nitride compared to etching the dielectric material, such as silicon dioxide. The two-step etch process and highly selective etch of silicon nitride add a level of complexity to such processing that is undesirable.
Accordingly, new methods are desired for forming conductive connections between first and second metal layers in semiconductor devices that reduce oxidation of copper without introducing undue complexity to processing.
In one aspect of the invention, a conductive connection forming method includes forming a first layer comprising a first metal on a substrate and transforming at least a part of the first layer to a transformed material comprising the first metal and a second substance different from the first metal. A conductive connection may be formed to the first layer by way of the transformed material. The method may further include forming a second layer comprising a second metal different from the first metal on the first layer. The transformed material may be an alloy material comprising the first and second metals. The alloy material may be less susceptible to formation of metal oxide compared to the first metal. By way of example, transforming the first layer may comprise annealing the first and second layer. An exemplary alloy includes an intermetallic. An exemplary first metal comprises copper, and an exemplary second metal comprises aluminum, titanium, palladium, magnesium, or two or more such metals.
Further, another aspect of the invention includes a conductive connection forming method wherein a first layer comprising copper is formed over a substrate. A second layer of a second metal different from the copper may be formed over the first layer. At least some of the second metal may be incorporated into an intermetal layer comprising the second metal and copper. The method further includes removing at least a portion of any second metal not incorporated into the intermetal layer and exposing the intermetal layer. A conductive connection may be formed to the intermetal layer.
Such, methods may be used as oxidation reducing methods or methods for protecting metal containing material from oxidation during semiconductor processing. Such methods are also conducive to use in methods of forming integrated circuit interconnects or integrated circuit wire bonds.
In another aspect of the invention, an integrated circuit includes a semiconductive substrate, a layer comprising a first metal over the substrate, and a layer of alloy material within the first metal comprising layer. The alloy material layer may comprise the first metal and a second metal different from the first metal. A conductive connection may be formed on the alloy layer.